Furcellaran as an antistatic agent for photographic film



United States Patent 3 184 311 FURCELLARAN AS Ahi AlQTlSTATIC AGENT FOR PHOTOGRAPHIC FILM Wilho M. Salminen, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Mar. 9, 1962, Ser. No. 178,547 9 Claims. (Cl. 96-85) This invention relates to photographic film, and more particularly to a film protected against static charges.

The accumulation of electrical charges on photographic film has been the cause of considerable diificulty in the past. In the ordinary handling operations, which occur in connection with the manufacture of sensitized photo graphic film, the film is passed over rollers, slides, and the like which result in the accumulation of static charges. When these static charges reach a sufficiently high intensity, a discharge can occur resulting in static lines on the sensitized film, which render the product unsuitable. Inasmuch as it is very difiicult to determine whether films has been damaged by static charges until after it has been exposed and processed, it has been extremely desirable to protect the film from this accumulation.

Various methods have been used for protecting photographic film and paper against static charges by incorporating certain ionic organic materials including water soluble materials as described in Morey and White, US. 2,639,234. The use of water soluble inorganic acid salt has also been proposed. In addition, materials which absorb water and therefore provide a conductive surface have recently been employed. Most of these methods have not proven entirely satisfactory with the newer highspeed emulsions or with the different film types now being manufactured.

In addition to the requirements for static charge dissemination due to the conductivity of the antistatic agent, it is necessary to have a substance which is relatively inexpensive, which is effective in small amounts, and which is not detrimental to photographic emulsions.

We have found a material which can be used for protecting a sensitive photographic film against static charges and can also be incorporated in a photographic paper for the same purpose. This material is obtained from red alga and is known as furcellaran.

One object of this invention is to provide a novel and protective means of guarding against static. Another object is to provide a method of coating a photographic element in order to reduce its static tendency. A further object is to provide a suitable means for protecting cellulose acetate films, especially cellulose triacetate films against static. Still another object is to provide a means of producing photographic film of considerably lower electrical resistance while at the same time, retaining its optical transparency. Other objects will appear from the following descriptions of my invention:

The above objects are accomplished by coating photographic film base with furcellaran. This material forms a clear film, when coated as a 0.5-l.0% solution. This is coated on the film support at a preferred rate of about 120 milligrams per square foot. At least 50 milligrams per square foot is required, and it can be used as high as 1 gram per square foot.

Material may also be coated on photographic paper base in the same concentrations and may be incorporated in the photographic emulsion up to 50l00% based on the weight of the vehicle or coated on the reverse side of the support in the same concentrations of 50 milligrams to 1 gram per square foot.

Furcellaran is a potassium salt of the sulfuric ester of a high molecular weight polysaccharide. Typical analysis "ice a sir reveals a polysaccharidc content between 63 and 68%, the rest being essentially water plus potassium and calcium salts.

Furcellaran is commercially obtained from the red alga Furcellaria fastigiata which is found primarily in northern European waters, especially in the 600 square-mile area between Denmark and Sweden known as the Kattegat. The weed floats free and grows at depths of 20-30 feet. Trawlers collect the alga with nets, although some of the alga drifts on shore and is also collected for processing.

The furcellaran is extracted by setting the red alga out to bleach in the sun for three days after which it is preserved in lime for about three weeks. The material is then neutralized to remove impurities and to prepare the furcellaran in a soluble state for extraction.

The material is gelled and then frozen. When thawed, water and other impurities separate first leaving furcellaran behind. This product is then bleached and prepared for packaging.

The commercial furcellaran is a white odorless powder that is soluble in hot or warm water, forms gels at a low concentration and is extremely viscous; it is also relatively stable to heat.

The following examples are intended to illustrate my invention but not to limit it in any way:

Example 1 Two grams furcellaran is dissolved with stirring in 200 cc. hot water. A clear solution is formed. One cc. saponin solution (153.4 gms./ 1000 ccs. distilled water) is added as a coating aid. This is coated onto a subbed cellulose triacetate film support with a hand coater, at the rate of 120 milligrams of furcellaran per square foot.

Example 2 A dyed gelatin peloid is coated with a furcellaran antistatic coating as described in Example 1.

Example 3 A clear gelatin peloid is coated with a furcellaran coating as described in Example 1.

The following table shows the surface resistivity of the coated layers.

Surface resistivity at Results: 50% RH, 10 ohms Subbed film support 10,000

Dyed gelatin peloid 21 Clear gelatin peloid 144 Furcellaran on subbed film support .017 Furcellaran on dyed gelatin peloid .091 Furcellaran on clear gelatin peloid .19

Example 4 Other polymeric films useful as film supports are coated with furcellaran at the rate of 100 milligrams per square foot. These film supports include polyethylene, polypropylene, cellulose acetate butyrate, cellulose acetate, cellulose nitrate, polyethylene terephthalate, and polystyrene. The resulting surface resistivities have an average value of 0.025 l0 ohms.

Example 5 Photographic paper is provided with an antistatic treatment by coating the paper with a concentration of milligrams of furcellaran per square foot and is found to have an average surface resistivity of 0025x10 ohms. Satisfactory results are obtained by coating the furcellaran on the same side of the photographic paper as the photographic emulsion and also by coating the furcellaran on the reverse side of the paper.

3 Example 6 Photographic paper having thereon a'water-resistant coating is provided with an antistatic treatment by coating the paper'with furcellaran in an amount of 1 gram per square foot. Satisfactory surfacefresistivities of less than ohms are obtained when the coating is applied on the ing is applied on the paper prior to applying over the coating the Water-resistant polymeric coating. Satisfactory surface resistivities are also obtained by coating the furcellaran. over the water-resistant coating layer. coatings which are used to render the photographic'paper Water resistant include-polystyrene, styrene-butadiene copolymers, vinylidenechloride-vinylchloride copolymers,

polyethylene, polycarbonate, cellulose ester, and the like. Someof these polymeric coatings may require: surface treatment such as electron bombardment, oxidation, and/ or a subsequent subbing to obtain adhesion. 'However, these surface treatments or subbing coatings do not interfere with the effectiveness of the furcellarancoating as 1 long as the yare compatible with photographic emulsions.

The surfaces which are useful for carrying the photo graphic emulsionand which can be employed with furcelharm as an antistatic coating include those mentioned above as well as paper and the other polymeric materials which can be formed intosuitable supports. These include polyesters, polycarbonates, polyolefins,; polyacrylates, icellulose esters,-,c'ellulo se ethers, and the like.

Any type of polymeric material'which can be used as a film supportis operable in my invention, and the particular type of support is not critical.

Furcellaran can be coated on a film support .on either p side and isnotremovable during .the processing steps so that it is a'permanentantistatic layer. The use of a permanent antistatic layer of this type aids in protecting the film during its passage in the film handling mechanism in the camera itself. Moreover; after the film has been processed, particularly in connection with motion-picture film, the processed film hasantistatic protection. This isparticularly helpful in avoiding attraction to the film Polymeric reverse side of the paper support and also when the coat- I claim: a I 1. A photographic film comprising a support having thereon a coating of furcellaran in an amount of 50 milligrams per square'footand also having thereon a lightsensitive silver halide emulsion layer to 1 gram per square foot. Q r

2. A photographic film comprising a film support having thereon a coating of furcellaran, to impart antistatic properties thereto. inan amount of 50 milligrams to 1 gram per square footand also having thereon a light sensitive silver halide emulsion layer.

3. A photographic paper comprising a paper-base having thereon a coating of furcellaran in an amount of 50 milligrams per square foot and also having thereon a light-sensitive silver halide emulsion layer to 1 gram per square foot. 7

. 4. A photographic film comprising a film support having thereon-a coating of furcellaran in an amount of 50.

milligrams per squarefoot .andalso having thereon a light-sensitive silver halide emulsion layer to 1 gram per a square foot;

.a layer; thereon of light-sensitive silver halide dispersed in a carrier, said layer containing fill-100%, based on the weight ofQthe carrier, of fu'rcellaran.

8.1 Photographic paperbase having a layer thereon'of light-sensitive silver halide dispersed in gelatin, said layer containing 50-100%, based on the Weight of the gelatin,

of dirt and dust particles which are picked up by charged motionpicture film supports.

a The. surface: resistivityis measured byplacing two f parallel electrodes on the film'ata fixed relative humidity of these electrodes are long compared to the distance between-them so asto avaid end effects. The-observed resistance readingis divided by the distance between electrodes and multiplied by their length to obtain the surface resistivity. I

A surface resistivity below 10 ohms has been determined as a value which is sutficient to alleviate difiiculties from static'electricity generated in the normal handling of sensitive filin. Furcellaran-has an average surface resistivity of 0.025 X 10 ohms whichv indicates itssuperior characteristics. a w V The invention has been described in considerabledetail with particular reference to preferred embodiments thereof, but it will be understood that variations. and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims. H n

of-furcellaran..

9. Photographic film base having a layer thereon of light-sensitive silver halide dispersed in gelatin, said layer containing 50-l0 0%, based on the weight of the gelatin, of furcellaran.- V I References Cited the Examiner r UNITED STATES PATENTS 2,639,234... 5/53 'Morey et al. 9687 2,725.29] 11/55 Morey 9687 3,053,662 9/62 Mackey' et all 9687 3,085,009 4/63 Chambers 96 84 Chambers 96-84 7 OTHER REFERENCES Whistler: Industrial Gums, TP978WS', pages 159 and 160.v L -f Economic Botany, vol. 1,3,N0. 4, October-December 1959, pages 365-370.

NORMAN G. Toacruw Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,184,311 May 18, 1965 hilho M. Salminen It is hereby certified t ent requiring correction and corrected below.

hat error appears in the above numbered petthat the said Letters Patent should read as Column 4, lines 1, II and 19, after "foot", insert to 1 gram per square foot and 6, l5 and 16 and lines 20 and 21, square foot", each occurrence.

each occurrence, same column 4, lines 5 strike out "to 1 gram per SEAL) Lttest:

ZRNEST W. SWIDER rttesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A PHOTOGRAPHIC FILM COMPRISING A SUPPORT HAVING THEREON A COATING OF FURCELLARAN IN AN AMOUNT OF 50 MILLIGRAMS PER SQUARE FOOT AND ALSO HAVING THEREON A LIGHTSENSITIVE SILVER HALIDE EMULSION LAYER TO 1 GRAM PER SQUARE FOOT. 